The phenomenon of biofouling is caused by the attachment of microorganisms such as bacteria to a wetted surface, which is followed by the attachment and growth of colonies of larger organisms on the surface such as plants algae or animals. Wetted surfaces are those exposed to water, moisture, humidity, water vapor, steam, condensation or ice.
Biofouling is a multistep process. Exposure of a surface or structure to water results in the adsorption of a film of dissolved organic material and colonies of bacteria appear and form a biofilm. In attaching to the surface, the bacteria release substances that provide mechanical stability through electrostatic forces such as hydrogen bonds and van der Walls interactions. As the attached bacterial cells begin to multiply, the biofilm thickens. This process is generally known as microfouling and enables the process of macrofouling. The formation of biofilms plays an important role in the next phase of biofouling known as macrofouling. Macrofouling is the attachment of larger organisms such as plants algae or animals. These larger organisms colonize biofilm coated surfaces and secrete a compound thought to be a hydrophobic glycoprotein biological adhesive which allows these organisms to become nearly permanently attached to a surface.
Biofouling represents a significant problem for any wetted surface or structure and may result in interference with the normal use and condition of the surface or structure. Such interference can lead premature break down of wetted structures and surfaces and can have significant economic implications to a number of industries.
In addition to interfering with the normal use and condition of wetted structures and surfaces, biofouling can in some cases also represent health and safety hazards due to the accumulation of microorganisms on a particular surface or structure.
Biofouling has a particularly significant impact on marine vessels. The outer hulls of marine vessels are an attractive habitat for algae and small life forms such as barnacles, which latch on and begin to form a layer of biological material attached to the ship. This phenomenon is known as “biofouling”. Biofouling is caused by the attachment of bacteria, which is followed by the attachment and growth of colonies of larger organisms on the surface.
Biofouling in a marine environment is also a multistep process. Within just minutes of placing a clean surface into seawater it adsorbs a film of dissolved organic material and colonies of bacteria appear within a few hours and form a biofilm. In attaching to the hull, the bacteria release substances that provide mechanical stability through electrostatic forces such as hydrogen bonds and van der Walls interactions. As the attached bacterial cells begin to multiply, the biofilm thickens and can reach as much as 500 microns in thickness. This process is generally known as microfouling and enables the process of macrofouling. The formation of biofilms plays an important role in the next phase of biofouling known as macrofouling. Macrofouling is the attachment of larger organisms such as mussels and barnacles. These larger organisms colonize biofilm coated surfaces and secrete a compound thought to be a hydrophobic glycoprotein biological adhesive which allows these organisms to become nearly permanently attached to a surface.
Once on a vessel's hull, biofouling results in an increase in overall surface roughness, which leads to an increase in hydrodynamic drag. The associated costs include increased fuel consumption, labour costs of cleaning a vessels' hull, as well as removing and replacing damaged paint, in addition to costs associated with the downtime required for such services. Studies have found that biofouling may result in a 10% increase in a vessel's drag, which in turn results in a 40% increase in fuel consumption. Existing antifouling solutions include tin and copper compounds added to a vessel's paint coating. Although initially effective, these compounds are inadequate as they leach out of the cured paint coatings of vessels resulting in limited prevention, inhibition, delay, alleviation or reduction of biofouling and have been shown to be harmful to aquatic life. Removal of this biofouling material often requires mechanical efforts as well as refinishing (e.g. painting). Such efforts require docking the vessel and in some cases dry docking the vessel. All of this results in costly downtime of the vessel.
Accordingly, more and better ways of hindering or delaying the biofouling process on wetted surfaces are desirable.